DMG: Are you planning on using two of the original CAT battery boxes for your D-6? Some of us just use a battery box from a later SA type machine, that will hold two 12V batteries. Whatever you do, I am sure will look good on your nice D6. JM

Juiceman, My end game will be two battery boxes built to look like the battery compartments on my D5 complete with a tool storage door under the battery compartment.  For now I will run 12V using the repaired 6V box that came on the tractor. I will post pics of that box soon.
 

Is anybody making reproductions of the battery boxes for tractors with the 6 volt pony motor?

Have not seen reproduction boxes. Mostly have to collect trashed boxes to get enough good parts to build one good one. A new bottom can be made and installed in 4 - 6 hrs. Seems many are without lids which rots the bottom after years in the rain. I am going to build a press brake attachment for my cheap 20ton press and see if I can bend up a new lid. In the attached pic you can see all of the parts that go into a complete box.